Circuit breaker



Feb.=23,` 1943. J Q JACKSON 2,312,169

CIRCUIT BREAKER Filed July 28, 1941 1 2 Sheets-Sheet l Y :UI tfalnr/IgIc/lgn ATTORNEY Feb. 23, 1943. J. G. JACKSON CIRCUIT BREAKER 2Sheets-Sheet 2 Filed July 28, 1941 INVENTOR r/a crson ff Patented Feb.23, 1943 CIRCUIT BREAKER John, G. Jackson, Detroit, Mica, assignmtoDetroit, Mich., a corpora- Square D Company, tion of Michiganappucationlulyas, 1941, serial No. 404,300

claims. (ci. 20o-ss) This invention relates to automatic electriccircuit breakers and more particularly tol the current responsivetripping means for effecting the automatic opening of such circuitbreakers upon current overload: vOne object of the present invention isto provide a simple and economical but eiective combined thermai'andmagnetic tripping means' for an automatic electric circuit breaker.

-Another object of this inventionxis to pr vide tripping means for anautomatic electric cir uit breaker including a current responsivebimetallic member having supported thereon a latching A compressionspring I4 is disposed between the bottom oi' the base I and the. bar 1to bias the Same.

surface movable bodily with the bimetallic mei'n-A s ber and alsomovable magnetically independent' of the bimetallic member into areleasing position.

Another object ofthe invention is to provide a current responsivebimetallic element with a Figure 3 is a detail sectional view on thelinev III-III of Figure 1.

Figure 4 is a detail' sectional view on the line IV-IV of Figure 1.

Figure 5 is a partial vertical sectional view of a modification.

The present invention has been illustrated in connection with a circuitbreaker mechanism which comprises a base I having a'conducting strap 2mounted on one end ledge thereof and carrying at its interior end astationaryscontact l. the connector 2 extending through an opening in aber plate 4 which closes the end of the base. Exterior of the plate 4 isa terminal connector I for the 'attachment of circuit wiring. Guided`for rectilinear movement within the base is a generally U-shaped element-6 upon whose long leg ispivotallyl mounted.l by interengaging notches',a contact bar 'I carrying at one end a movable contact 8 cooperatingwith the stationary contact 3. Fiber plates indicated at 9 combine withthe plate 4 to enclose the contacts 3 and l within an arcing chamber. Anoperating handle is provided at II pivotally vmounted upon a shaft I2and having a cam surface I3 cooperating with the ilat surface of themember 8 to etiect manual movement of the contact bar 1.

The lower end ofthe base'is provided with an vend facing terminalcomprising a conducting connector I5 inserted in slots inthe oppositeside' walls of the base from the front. and mainltained against endwiseremoval by both a terminaLscrew I9 and an adjusting stud I1. Amidportion of the connector is pressed outwardly at I8 to take up anyslack or play in the connector mounting. A tab I9 is pressed out of theconnector and the stud I1 is threaded into the tab I9 to provide foradjustment of the free end of a bimetallic member 2I welded on the endof the connector, thus providing for adjustment of the calibration ofthe breaker. Embracing the bimetallic element 2| is a magnetic'yoke 22which is of generally U-shape and which has a widenedl forward extensionat 23 received within slots in the opposite side walls of the base tomount the yoke, as more particularly shown in Figure 2. A magneticarmature element 24 ls provided having a central slot 25 through whichthe latching end ofthe contact bar passes in its automatic tripping andresetting movements.

The upper end of the armature is provided with a widened flange 26received in slots in the opposite side walls of the base and serving topivotal- 1y support the armature for swinging movement about the point21. Mounted upon the bimetallic member 2I is a resilient spring strip 28welded to an intermediate point on the bimetal and extending in oppositedirections. At the free end of the bimetal, the strip 29 is formed toprovide a latching tip at 29 biased by its resiliency away from theplane of the bimetal but having its latching position limited by theengagement oi' flange II with the lower face of the bimetal. TheVopposite end of the strip 28 bears against the armature 24 as at 32 tobias it into its unattracted position whose limit is determined by astop on the base.

The circuit breaker mechanism, as shown In full lines in Figure 1, is init's normally operating 'closed circuit position. The dotted lines ofthe mechanism indicate the automatic tripped position inwhich .thecircuit through the breaker is open upon the occurrence of an excesscurrent condition. The breaker is reset into latched position bymanipulation of the operating handle II andthe contacts are moved totheir manual on and oii'" positions for normal switching operation alsobymanipulation of the handle I I, the operation of the mechanism itselfbeing more fully described in my Patent No.

2,096,546 but with the handle operation described in my Patent No.2,096,545, both issued October 19, 1937. 'Ihe operation 'of the trippingmechanism is as follows:

non,

facteur Y direction into the For low current overloads of continueddural dotted line position of `Figure 1. Upon the occurrence of heavieroverloads,

'I which then rotatesin a clockwise the magnetic elements of thetripping means operate quicker thannormal thermalexing of the bimetal 2|to effect the tripping' ofthe mecha anism in a shorterv elapsedtimgthanwould be taken by the bimetal alone. Whentheux induced in themagnetic circuit formed'by the yoke'y 22 and the armature 24 becomessufilcient, the

armature rotates in a clockwise direction and strikes the latching tip29, moving it downwardly against its resilient biasy into-unlatchingposi-` tion. This movement ontneiathing tip 29 may be effected withoutmovement-of the bimetal 2|. so that the only resistance offered to themagnetic movement is the resilient bias in the spring 29.

While the operationpf the tripping means for the Vbreaker has beendescribed in termsv of thermal or magnetic effects operating separately,it is, of course, possible that they may have a combined operation withthe'magnetic forcey insumcient tommove the latchingl tip alone, butwhere the combined flexing of the bimetal and the magnetic force aresuillcient to effect the unlatching movement of the latchingtip.

V"`\In` previ'ous constructionswhere the contact bar was latcheddirectly to the end of the bimetal, it was found desirable to grind theend vof the bimetal into a smooth latching-surface. The.use of the strip28 even without the magnetic elements 'of the tripping means isadvantageous in substituting tesimple strip mounting for the ratherexpensive grinding operation;

In the modified form of the invention illus trated inFigure 5; a modiedmagnetic circuit is provided. 'This construction shows a connector33mounted upon a lower end ledge pro vided on` the breaker base andextending within the breaker where it is provided with a pressed.

out tab 34 on which a corrugated bimetal 35 is welded. A -cross-piece 39receives theadjusting screw 31. Theinterior end of the bimetal isprovided with a resilient metal strip 38 formed to `provide the latchingtip 39. The magnetic circuit comprises a magnetic L-shaped piece 4|whichg carries a pole piece 42 about which is wrapped the flexiblel lead43 which interconnects the bimetal 35 and the Vcontact bar A resilientspring hook is provided at-43 mounted at the end of the L-shaped member4|, which hookextends through an opening 44 in an armature member 45,the hook 43 servingg not only to retain the amature 45, but also to biasit into its unattracted position. At one side only of the arma-v ture45there is provided a finger 46 positioned to engage the latching tip 39eccentrically of Iits axis to effect its movement into unlatchingposition. It havsbeen 'found that the use of a singlei 55,

side finger facilitates the movement ofthe latchirg tip intounlatchingposition with a lower magnetic force than is required if a balancedforce at both sides of the tip is exerted. The operation of thistripping unit is substantially the same as that previously described.

While this invention has been described in connection with a particularcircuit breaker mechanism to show a complete operative structure, it isunderstood that the tripping means 75 effecting engagement andseparation of said oontacts at will, and means automatically releasableto effect separation of said contacts, current responsive means foreiecting the release of said releasable means upon the passage of anoverload current through the circuit breaker comprising a bimetallicmember heated in response to the flow of current through the breaker,and

a thin metal strip mounted on said bimetallicmember and formed about anend thereof` to provide a latching surface engaged by said re,- leasablemeans in a direction to apply a compres,- sive force along the length ofthe main'portion of said bimetallic member, said member :dexing whenheated by the passage of an overload current through the circuit breakerto bodily --move said latching surface into releasing position.-

2. In an automatic electric circuit breaker having separable contacts,manual means for effecting engagementand separation of said contacts atwill, and means automatically releasable to effect separation ofsaidcontacts, currentv responsive means for eecting the release of saidreleasable means upon the passage of an 4overload current throughV thecircuit breaker com,- prising a bimetallic member heated in response tothe flow of current through the breaker, a resilient spring stripmounted on saidmember and formed to provide a latching surface biased bylits inherent resiliency to a predetermined Vposition with respect tosaid bimetallic member,.

er'to bodily move said latchingsurfaceinto re-` l leasing position.

3. In an automatic .electric circuit breaker having separable contactsand means releasable to efectseparation' of said contacts,7 currentresponsive means for effecting the release of said releasable means uponthe passage of an overload lcurrent through the circuit breaker com.-prising av bimetallic member heated in response to'the ow ofA currentthrough thebreaker, a resilient-spring striplmounted on said member yand formed toaprovide. a latching surface biased by its inherentresiliency to' a predetermined positionwith respect to said bimetallicmember, said bimetal flexing when-heated to bodily move said'latchingsurface into releasing position, and

magnetic means for eifecting movement "of said latching surface againstits resilient bias and relative to said bimetallicv member intounlatching position',saidmagnetic means being energized in responsel tothefiow of current through the breaker.

4. In an automatic electric circuit breaker having separable-contactsand means releasable to effect separation of said contacts, currentresponsive means for eifecting the release of said releasable means uponthe passage of an overload current through the circuitbreakergcomprising a bimetallic member heated in response to the flow ofcurrent through the breaker, a magnetic yoke, means energizing said yokein response to the flow of current through the breaker, an armaturemember adapted to be attracted to said yoke upon the passage of anoverload current, a resilient spring strip mounted on said bimetallicmember and formed to provide a latching tip biased to a predeterminedposition with respect to said member by the inherent resilience of saidstrip, said bimetallic member ilexing when heated to bodily move saidlatching tip into unlatching position, said armature, when attracted,engaging and moving said latching tip against its resilient bias intounlatching position independent of movement of the bimetallic member.

5. In an automatic electric circuit breaker having separable contactsand means releasable to effect separation of said contacts, currentresponsive means for eifecting the release of said releasable means uponthe passage of an overload current through the circuit breakercomprising a bimetallic member heated in response to the flow of currentthrough the breaker, a magnetic yoke, means energizing said yoke inresponse to the flow of current through the breaker, an armature memberadapted to be attracted to said yoke upon the passage of anv overloadcurrent, a resilient spring strip mounted on said bimetallic member andformed to provide a latching tip biased to a predetermined position withrespect to said member by the inherent resilience of said strip, saidbimetallic member flexing when heated to bodily move said latching tipinto unlatching position, said armature, when attracted, engaging andmoving said latching tip against its resilient bias into unlatchingposition independent of movement of the bimetallic member, the end ofsaid spring strip remote from said latching tip being formed to engagethe armature to bias it into its unattracted position. Y

6. In an automatic electric circuit breaker having separable contactsand means releasable to effect separation of said contacts, currentresponsive means for effecting the release of said releasable means uponthe passage of an overload current through the circuit breakercomprising a serially connected bimetallic member traversed by thecurrent passing through the breaker so as to be heated thereby, amagnetic yoke embracing said bimetallic element so as to be energized bythe current traversing the same, an armature member adapted to beattracted to said yoke upon the occurrence of an overload current, aresilient spring strip mounted on said bimetallic member and formed toprovide a latching nose biased tov a. definite position with respect tothe plane of the bimetallic member, the flexing of said bimetallicmember, when heated, bodily moving said latching nose to releasingposition, said armature, when attracted, engaging and moving saidlatching nose against its resilient bias into releasing positionindependent of the movement of the bimetallic member. A

7. In an automatic electric circuit breaker having separable contactsand means releasable to eiect separation of said contacts, currentresponsive means for effecting the release of said releasable means uponthe passage 'of an-overload current through the circuit breakercomprising a bimetallic member heated in response to the flow of currentthrough the breaker, a resilient spring strip mounted on said member andformed to provide a latching surface biased by its inherent resiliencyto a predetermined position with respect to said bimetallic member, saidbimetal flexing when heated to bodily move saidv latching surface intoreleasing position, magnetic means for effecting movement of saidlatching surface against its resilient bias into unlatching position,said magnetic means beingA ener-r gized in response to the flow ofcurrent through the breaker, and exerting its force on the latching tipeccentrically of the axis of the spring strip.

8. In an automatic electric circuit breaker having separable contactsand means releasable to effect separation of said contacts, currentresponsive means for effecting the release of said releasable means uponthe passage of an overload current through the circuit breakercomprising a bimetallic member heated in response to the flow of currentthrough the breaker, a magnetic yoke, .means energizing said yoke inresponse to the flow of current through the breaker, an armature memberadapted to be attracted to said yoke upon the passage of an overloadcurrent, a resilient spring strip mounted on said bimetallic member andformed to provide a latching tip biased to a ,predetermined positionwith respect to said member by the inherent resilience of said strip,said bimetallic member flexing when heated to bodily move said latchingtip into unlatching position, said armature, when attracted, engagingand moving said latching tip againstk its resilient bias into unlatchingposition inde-Y- pendent of movement of the bimetallic member, saidarmature engaging said latching tip with its line of force directedeccentrically of the axis of the spring strip.

9. In an automatic electric circuit breaker having separable contacts,manual means for effecting engagement and separation of said contacts atwill, and means automatically releasable to effect separation of saidcontacts, current responsive means for effecting the release of saidreleasable means upon the passage of an overload current through thecircuit breaker comprising a bimetallic member heated in response to theflow of current through the breaker, a resilient spring strip non-selfmovable 'in response to temperature change mounted on said member andformed about an "end thereof to provide a latching surface engaged bysaid releasable means, said member flexing when heated by the passage ofan overload current through the circuit breaker to bodily move saidlatching surface into releasing position.

10. In an automatic electric circuit breaker having separable contacts,manual means for effecting engagement and separation of said contacts atwill, and means automatically releasable to effect separation of saidcontacts, current responsive means for effecting the release of saidreleasable means upon the passage of an overload current through thecircuit breaker comprising a bimetallic member heated in response to theflow of current through the breaker, a resilient spring strip mounted onsaid member and carrying a latching surface engaged by said releasablemeans, saidy member flexing when heated by the passage of an overloadcurrent through the circuit breaker to bodily move said latchinglsurface into releasing position, said latching surface being movablerelative to said member against the resilient bias of said spring strip.

. JOHN G. JACKSON.

